v3.0.0

Breaking Changes:
- Function signature of SignURL in security package has been updated. The argument tokenID has been replaced with accessKey. Access key for a token can be found by going to console.pixelbin.io > Settings > Tokens > Click on any Token > Access Key.
- Package name has been updated to reflect the url where its located now
github.com/pixelbin-dev/pixelbin-go => github.com/pixelbin-io/pixelbin-go